Tissue growth control apparatus and method

ABSTRACT

A method and apparatus for providing germicidal and healing treatment of tissue such as bone wherein an electrode of silver or like material is applied to a living tissue site to be healed, initially a direct voltage is applied to the electrode of a polarity driving the electrode as an anode to release silver ions to create a germicidal environment at the site, and thereafter a direct voltage of opposite polarity is applied to the electrode driving it as a cathode to stimulate healing of the tissue at the site. The apparatus is implanted in the body of a patient, and in one embodiment a battery is connected through a switch to the electrode and a reference electrode, the switch initially connecting the electrode as an anode and thereafter changeable by an external operator such as a magnet to connect the electrode as a cathode. In another embodiment, another electrode and an element cooperate with the treating electrode to form a galvanic couple with the treating electrode to create a germicidal environment and a predetermined time thereafter the arrangement changes to a biogalvanic couple with body fluid to cause healing of the tissue. In either embodiment a wave shaping circuit can be operatively associated with the treating electrode to facilitate external monitoring of the apparatus when implanted.

BACKGROUND OF THE INVENTION

This invention relates to healing and growth control of tissue such asbone, and more particularly to a method and apparatus for providinggermicidal and healing treatment of tissue such as bone.

One area of use of the present invention is providing germicidal andhealing treatment of live bone at a bone graft site, although theprinciples of the present invention can be variously applied. Yasudafound in 1955 that a bone fracture area is a region of abnormally highelectrical negativity which appeared to be associated with healing, andhe along with Bassett found in 1964 that the application of an artificalelectric field from a battery accelerated the healing. Becker found in1963 and 1977 that silver electrodes, when driven positively, produce agermicidal environment, and he also found that electrical anodalcurrents of up to about 40 microamperes d.c. are beneficial for agermicidal effect but that negative electric currents of as little asone microampere d.c. are adequate for healing.

It would be highly desirably to provide a method and apparatus fortissue growth control which can accelerate the growth of living tissuesuch as human bone, and which also can create a germicidal environmentfor curing tissue and bone infections as well as inhibiting the growthof tumors.

SUMMARY OF THE INVENTION

It is, therefore, a primary object of the present invention to provide anew and improved method and apparatus for providing both germicidal andhealing treatment of living tissue such as bone.

It is a further object of this invention to provide such method andapparatus wherein the germicidal and healing treatment modes thereofoccur during distinct and precisely controllable time periods.

It is a further object of this invention to provide such method andapparatus wherein an effective germicidal environment is created at thetissue site whereupon an effective healing operation occurs thereafter.

It is a further object of this invention to provide such apparatus whichis implantable in the body of a patient.

It is a further object of this invention to provide such apparatus whichderives electrical energy for its operation through biogalvanic actionwith body fluids.

It is a further object of this invention to provide such apparatus whichis implanted and which is monitored readily from outside the body of apatient.

The present invention provides a method and apparatus for providinggermicidal and healing treatment of tissue such as bone wherein there isapplied to a living tissue site to be healed an electrode of a material,preferably silver, which releases ions to create a germicidalenvironment at the site in response to electrical current flow in onedirection relative to the electrode and which stimulates healing oftissue at the site in response to electrical current flow in theopposite direction relative to the electrode. Initially, there isapplied to the electrode a direct voltage of polarity causing thecurrent flow in one direction to drive the electrode as an anode andrelease ions to create the germicidal environment at the site.Thereafter, there is applied to the electrode a direct voltage ofopposite polarity causing the current flow in the opposite direction todrive the electrode as a cathode to stimulate and promote healing of thetissue at the site. The apparatus preferably is of the type which isimplanted in the body of a patient. In one embodiment thereof, a batteryis connected to the electrode and to a reference electrode under controlof a switch having a first state connecting the electrodes in a mannerestablishing the germicidal mode of operation and changeable to a secondstate under control of an external operator such as a magnet whichsecond state connects the electrodes in a manner establishing thehealing mode. In another embodiment thereof, the apparatus includes anadditional electrode and an element which cooperate to form a galvaniccouple with the treating electrode to establish the germicidal mode ofoperation and which after a predetermined time change to a biogalvaniccouple with body fluid to establish the tissue healing mode ofoperation. In either embodiment, a wave shaping circuit can beoperatively associated with the treating electrode to produce a currentwaveform which is readily discernible by external monitoring equipment.

The foregoing and additional advantages and characterizing features ofthe present invention will become clearly apparent upon a reading of theensuing detailed description together with the included drawing wherein:

BRIEF DESCRIPTION OF THE DRAWING FIGURES

FIG. 1 is a schematic diagram of apparatus according to the presentinvention;

FIG. 2 is a diagrammatic view illustrating the apparatus of the presentinvention in a typical application wherein it is implanted in the bodyof a patient adjacent a bone graft site;

FIG. 3 is a diagrammatic view of apparatus according to anotherembodiment of the present invention;

FIG. 4 is a diagrammatic view of the apparatus of FIG. 3 implanted inthe body of the patient adjacent a bone graft site; and

FIG. 5 is a schematic diagram of a monitoring scheme useable with theapparatus of the present invention.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Referring now to FIG. 1, the apparatus 10 of the present invention forproviding germicidal and healing treatment of tissue such as bonecomprises a treating electrode in the form of a lead or wire 12 adaptedto be placed in operative contact with a living tissue site to behealed. The treating electrode 12 is of a material which releases ionsto create a germicidal environment at the site in response to electricalcurrent flow in one direction relative to the treating electrode 12 andwhich promotes healing of tissue at the site in response to electricalcurrent flow in the opposite direction. According to a preferred mode ofthe present invention the wire 12 is of silver. A portion of the lengthof wire 12 is enclosed by a protective covering or sheath 14 of humanbody reaction-free material such as a suitable silicone rubber material.The sheath 14 serves to allow operative contact between the wire 12 andbody tissue only at the site where healing is to take place. Theapparatus further comprises another electrode adapted to be connected ata location spaced from the site to be healed. In the apparatus shown inFIG. 1, this electrode is designated 16 and will be described in furtherdetail presently.

The apparatus 10 of the present invention further comprises means forestablishing an electrical current flow path between the electrodes andmeans for applying direct voltage of one polarity to the treatingelectrode 12 to cause electrical current flow in the one direction tocreate a germicidal environment at the tissue site and after apredetermined time to apply direct voltage of the opposite polarity tothe treating electrode to promote healing of tissue at the site. Inparticular, the apparatus includes a direct voltage source in a form ofa battery 20 having positive and negative polarity output terminals 22and 24, respectively. Battery 20 is of the type capable of deliveringover 2.0 volts, and one form of battery 20 is a lithium-iodine batteryof implantable grade and hermetically sealed for use with artificalcardiac pacemakers, available commercially from Wilson Greatbatch Ltd.of Clarence, N.Y. and designated model 752. A switching means isoperatively connected to the electrodes and to the terminals of thesource. In particular, the switching means comprises a first switch arm28 movable between a pair of switch contacts 30 and 32. The switchingmeans further comprises a second switch arm 34 movable between a pair ofswitch contacts 36 and 38. The broken line 40 extending between theswitch arms 28 and 34 indicates that the switch is of the type wherebythe two switch arms 28 and 34 are moved in unison or togethersimultaneously between positions engaging the two sets of contacts. Inparticular, the switching means has a first state wherein switch arm 28engages contact 32 and switch arm 34 engages contact 38. The switchingmeans has a second state wherein the switch arms 28 and 34 are movedinto positions engaging the contacts 30 and 36, respectively. One formof the switching means comprises two implanted single pole, double throwmagnetic reed switches driven by a common extracorporeal permanentmagnet of the type commonly used with implanted demand cardiacpacemakers to shift the pacemaker from a demand to an asynchronous mode.By way of example, such switches are available commercially from GordosCorp. of Bloomfield, N.J. under part no. MR 5204-1. The magnet can beany commercially available permanent magnet of the small, hand-heldtype.

The positive terminal 22 of battery 20 is connected by a lead 42 toswitch contact 30. The positive terminal also is connected by a lead 44to one terminal of a resistor 46, the other terminal of which isconnected to switch contact 38. The negative terminal 24 of battery 20is connected by a lead 48 to switch contact 32. Negative terminal 24also is connected by a lead 50 to one terminal of a resistor 52, theother terminal of which is connected to the switch contact 36. Thus, theswitching means has a first state wherein the silver electrode 12 isconnected through resistor 46 to the positive terminal 22 of battery 20so as to be driven as an anode and the other or reference electrode 16is connected to the negative terminal 24 of battery 20, and a secondstate wherein the silver electrode 12 is connected through resistor 52to the negative terminal 24 of the battery so as to be driven as acathode and the other or reference electrode 16 is connected to thepositive terminal 22 of the battery. When the switching means is in thefirst state the current flow is in a direction relative to the silverelectrode 12 causing silver ions to be released to create a germicidalenvironment at the tissue site, and when the switching means is in thesecond state the current flow is in an opposite direction relative tothe electrode 12 causing healing of the tissue at the site.

By way of example, in an illustrative device battery 20 delivers anoutput voltage of 2.8 volts, resistor 46 has a magnitude of about 150kilohms, and resistor 52 has a magnitude of about 2 megohms. Electrode16 is integral with the outer casing 56 or can of the battery 20 whichcasing 56 is of electrically conductive material such as stainlesssteel. Accordingly, electrode 16 operatively contacts neighboring bodytissue through the contact of the casing 56 with such tissue. Whenswitch arms 28 and 34 are moved by the magnet into positions engagingthe contacts 32 and 38, respectively, the silver electrode 12 is drivenas an anode and a positive germicidal current of about 15 microamperesis delivered through the electrode 12 to the tissue site. After apredetermined time the magnet is removed and the switch arms 28 and 34move to their normal positions engaging the switch contacts 30 and 36thereby driving the electrode 12 as a cathode. In this mode a negativehealing current of about 1.0 microampere is delivered through the silverelectrode 12 to the tissue site.

In one form of the apparatus, the components including the switchingmeans, resistors 46,52 and leads are assembled and arranged on the topor lid of the battery 20 and then cast into a body of suitable epoxymaterial such as Scotchcast V or the equivalent. Alternatively, thebattery 20 and remaining components including switches, resistors andleads are placed in another enclosure or container of metal which thenis hermetically sealed. The outer metallic enclosure or container wouldbe, for example, of titanium or stainless steel and provided withhermetic feed through terminals of glass or ceramic material. Theapparatus typically is implanted in the body tissue of a patient, andshould long-term implantation be considered, the anodal corrosion of thestainless steel or titanium reference electrode might be objectionable,in which case the reference electrode could be of platinum. While thepresent example considers the metallic casing or can as the referenceelectrode, the can could be left "floating" electrically and a separatereference electrode such as a platinum wire would be provided. When theapparatus is implanted in the body tissue of a patient, the switchoperating magnet is externally applied to the adjacent region of thepatient's body and held in place by a bandage or similar holding means.The magnet is held in position for a predetermined time, for exampleseveral days to place the apparatus in the germicidal mode. Then themagnet is removed to reverse the voltage polarity of the output of theapparatus thereby switching the operation to a healing mode. Theapparatus then remains in the healing mode for the required time, whichcan be approximately twelve weeks for healing simple fractures to aslong as up to about 12 years when controlling pseudoarthritis of thetibia bone. The latter condition occurs congentially in children andresults in periodic breakage of the tibia bone. After puberty thecondition spontaneously disappears.

FIG. 2 illustrates a typical application of the apparatus of the presentinvention for providing germicidal and healing treatment at a bone graftsite. The clinical procedures are described in further detail by Becker,Spadero and Marino in "Clinical Experiences in Low Intensity DirectCurrent Stimulation of Bone Growth", Journal of Clinical Orthopedics,124:75, 1977. A live bone 60 which has been fractured or otherwisebroken into two sections 60a and 60b is located within the body tissue62 of a patient. The live bone sections 60a and 60b have medullarycavities 64a and 64b, respectively. Between the fractured or broken endsof the bone sections 60a and 60b there is inserted a dead bone graftsection 66 which has a medullary cavity 68. The spacing between thegraft section 66 and the adjacent ends of the live bone sections 60a and60b is exaggerated for convenience in illustration. The apparatus of thepresent invention, generally designated 10', is implanted in the bodytissue 62 of a patient at a location adjacent the bone graft site. Theapparatus is similar to that shown in FIG. 1 and identical componentsare provided with the same reference numeral having a prime designation.Battery 20' has an outer casing 56' of metal and in this particularillustration casing 56' is connected by a lead 70 to a referenceelectrode 72 implanted in tissue 62 at an adjacent location.Alternatively, the battery casing 56' may itself be the referenceelectrode. Components of the apparatus 10' including the switchingmeans, resistors and leads are encapsulated in a body of epoxy material74 which is formed on the lid of battery 20' adjacent the positive andnegative terminals 22' and 24', respectively. A passage or bore 78 isdrilled surgically or otherwise provided in the live bone section 60aleading from the exterior surface thereof into the medullary cavity 64a,the passage 78 extending at an acute angle to the longitudinal axis ofthe bone section. Similarly, another passage or bore 80 is provided inthe live bone section 60b extending from the external surface thereofinto the medullary cavity and disposed at an acute angle to thelongitudinal axis of the bone section. The silver electrode or wire 12'extends from the apparatus 10' through and along the passage 78, intoand along the medullary cavity 64a in a direction toward the bone graftsection 66, from the bone section 60a through the bone graft section 66and along the medullary cavity 68 thereof, into and along the medullarycavity 64b of the other live bone section 60b, and then into the passage80 provided in that bone section extending along the entire passage andterminating at the outer surface of the live bone section 60b. The sheetor covering 14' of protective material, such as silicone rubber, extendsfrom the body 74 of the apparatus to the outer surface of the live bonesection 60a so that this portion of the length of wire 12' is notexposed to the neighboring tissue 62. Thus, the remaining section of thesilver wire 12' is entirely exposed to the live bone sections 60a, 60band to the graft bone section 66. Alternatively, the exposed portion ofwire 12' could be placed directly in the fracture site, adjacent to theareas where healing is desired. This is because it may be either thecurrent field through the bone break or the voltage field around theelectrode 12 when driven as a cathode which is most effective inpromoting osteogenesis. In addition, bone chips or fragments might beused in the bone graft section 66 rather than a discrete bone segment.

After the apparatus 10' has been implanted and installed in theforegoing manner, a magnet is externally applied to the adjacent outersurface of the patient's skin over the apparatus 10'. The magnet is heldin place by a bandage or other suitable fastening means as previouslydescribed. This activates the two implanted reed switches placing theapparatus in the germicidal mode of operation wherein the positivecurrent having a magnitude of about 15 microamperes is driven into thesilver electrode 12' causing anodal corrosion of the silver and therelease of silver ions into the region of the bone graft. This creates agermicidal environment which clears the bone graft area of bacterialinfection. This release of silver ions also possibly clears the area oftumor cells according to the findings reported by Spadero in 1976.

After a predetermined time, which can range from about one day to aboutone week, the external magnet is removed with the result that the reedswitches move to their normal positions thereby placing the apparatus inthe healing mode of operation. In this mode, the voltage output polarityof the apparatus is reversed, and the electrical current output isreduced to a level of about 1.0 microamperes and the direction ofcurrent flow is reversed. The apparatus of the present invention has 1.5ampere hours of battery life and therefore can remain viable for over 10years. However, after adequate healing is obtained the apparatus couldeither be removed or simply left implanted innocuously in the bodytissue. Normal bone growth advances sufficiently to justify removal ofthe apparatus in about 12 weeks. Specialized cases, on the other hand,which heretofore were untreatable, could require up to 12 years ofstimulation, and the apparatus of the present invention is quite capableof doing that.

FIG. 3 illustrates apparatus according to another embodiment of thepresent invention. In this embodiment the apparatus includes a treatingelectrode, another electrode, and an element which serves to form agalvanic couple with the treating electrode to create a germicidalenvironment at the tissue site, whereupon a predetermined timethereafter the galvanic couple changes to a biogalvanic couple with bodyfluid and tissue to cause healing of the tissue site. In particular, theapparatus generally designated 90 in

FIG. 3 includes a treating electrode 92 adapted to be connected to aliving tissue site to be healed. The treating electrode is of amaterial, preferably silver, which releases ions to create a germicidalenvironment at the site in response to electrical current flow in onedirection relative to the treating electrode and which promotes healingof tissue at the site in response to electrical current flow in theopposite direction. According to a preferred mode of the presentinvention the electrode 92 is in the form of a thin silver wire. Theapparatus includes another electrode 94 adapted to be connected to alocation spaced from the site to be healed. According to a preferredmode of the present invention the other electrode 94 comprises aplatinum wire. The apparatus further comprises means for establishing anelectrical current flow path between the electrodes, and in theapparatus shown a resistor designated 96 is connected electrically inseries between the electrodes 92 and 94. As illustrated in FIG. 3, theresistor 96, electrical terminals thereof, and portions of the wires92,94 which are connected by soldering, welding or the like to theresistor terminals are encapsulated in a body 98 of epoxy material, forexample epoxy material commercially available under the designationScotchcast V. The body 98, in turn, is enclosed in a sheet or layer 100of human body reaction free material, for example Dow Corning SiliconType A medical adhesive material.

The apparatus of the present invention further comprises means forapplying direct voltage of one polarity to the treating electrode 92 tocause electrical current flow in the one direction to create agermicidal environment at the tissue site and after predetermined timeapplying direct voltage of the opposite polarity to the treatingelectrode to promote healing of tissue at the site. In particular, theapparatus includes a minute quantity or body of magnesium 104 which isjoined to the end or tip of the platinum electrode 94. Magnesium element104 can be joined to the platinum wire 94 in a suitable manner, forexample by dipping the end of the platinum wire 94 into a quantity ofmolten magnesium and then allowing the adhered quantity to cool andthereby bond to the tip of wire 94. The body of magnesium 104, beingvery chemically active, forms a strong galvanic couple with the silverelectrode 92, initially driving the silver electrode positive as ananode to a voltage of about 1500 millivolts measured open circuit. Themagnesium also is attacked by the warm physiological saline present inthe body tissue. A current of about 15 microamperes is delivered throughthe silver electrode 92 to the tissue site, the silver corroding andleaving a germicidal environment of silver ions at the site. Thiscorrosion together with the galvanic battery action is sufficient toconsume all of the minute amount of the magnesium body 104 in a fewdays. The amount is so small or negligible that the residual productsare carried away easily by the body circulatory system. Once themagnesium quantity 104 is consumed, the apparatus then automaticallyreverts to the healing mode wherein the silver wire 92 is driven as acathode, In particular, the silver electrode 92 and platinum electrode94 create a biogalvanic couple with the body tissue and the fluid whichcouple delivers about 250 millivolts measured open circuit to the silverelectrode 92 which is driven as a cathode in this mode. Resistor 96preferably has a magnitude of about 100 kilohms.

Thus, the apparatus 90 initially has an automatic germicidal modewherein about 15 microamperes of anodal current is delivered through thesilver anode 92 to the tissue site for a few days. The silver corrodesand leaves a germicidal environment of silver ions to remove anyinfection at the tissue site. After a few days in this mode, theelectrical polarity of the output of the apparatus automaticallyreverses. The silver electrode 92 automatically becomes a cathode andproceeds to heal the fracture at the tissue site over the requiredperiod of time. The series resistor 96 having a magnitude of about 100kilohms serves to limit the current to the range from about 10microamperes to about 15 microamperes in the germicidal mode and toabout 1 microampere in the opposite direction when the apparatus is inthe healing mode. By way of example, the magnesium body 104 has a weightof about 15 milligrams.

FIG. 4 illustrates the apparatus of this embodiment of the presentinvention in a typical application as it would appear implanted adjacenta bone graft site. A live bone 110 includes a first section 110a and asecond section 110b which have been separated or broken due to afracture. The bone 110 is within the body tissue 112 of a patient. Bonesection 110a has a medullary cavity 114a and , similarly, bone section110b has a medullary cavity 114b. Between the fractured bone sections110a and 110b a bone graft section 116 is positioned in a manner similarto that of the arrangement of FIG. 2, the bone graph section 116 havinga medullary cavity 118. The apparatus of this embodiment of the presentinvention, here designated 90', is anchored to the bone 110 near thefracture site. The apparatus 90' can be anchored by various suitablemeans, for example a pair of wires designated 120,122 in FIG. 4 whichare wrapped around the bone section 110b to secure the apparatus 90'thereto. The platinum wire or electrode wire 94' extends from the bodyof epoxy encapsulant along and in spaced relation to the outer surfaceof bone section 110b as shown in FIG. 4. The magnesium body 104' at thetip of wire 94' is free to float in the neighboring body fluid. A firstbore or passage 124 is provided surgically in bone section 110aextending from the outer surface thereof to the medullary cavity 114aand disposed at an acute angle to the longitudinal axis of bone section110a. Similarly, a bore or passage 126 is provided in bone section 110bextending from the outer surface thereof to the medullary cavity 114bthereof and disposed at an acute angle to the longitudinal axis of thebone section 110b. The silver electrode or wire 92' of the apparatusextends from the body of encapsulant through and along the passage 126to the medullary cavity 114b, further along in a direction toward thebone graft section 116 through the medullary cavity 18 thereof, and intothe medullary cavity 114a of bone section 110a. The wire 92' extendsfurther along the medullary cavity 114a and then enters and extendsalong the passage 124 in bone section 110a. The wire 92' terminatesadjacent the outer surface of the bone section 110a. Alternatively, bonechips or fragments might be used in the bone graft section 116 ratherthan a discrete bone segment.

FIG. 5 illustrates a monitoring arrangement for use with apparatus ofthe type illustrated in FIGS. 1-4. In particular, tissue growth controlapparatus of the type illustrated in FIGS. 1-4 operate with low leveld.c. currents, and this low level d.c. current operation rendersimplanted devices of this type difficult if not impossible to monitor bymeans of conventional external patient monitoring apparatus andprocedures. In accordance with the present invention, a wave shapingcircuit is operatively associated with the treating electrode tofacilitate external monitoring of the apparatus when implanted.Referring now to FIG. 5 there is shown implantable apparatus for healingtreatment of tissue such as bone comprising a treating electrode 140 ofa material which promotes healing of tissue in response to electricalcurrent flow relative to the electrode, and means generally designated142 for applying voltage to the electrode to cause the current flow. Forexample, the combination of treating electrode 140 and voltage applyingmeans 142 can represent the apparatus designated 10 in FIG. 1. In thearrangement of FIG. 5, the treating electrode, for example a thin silverwire as described in the previous embodiments, is shown in two sections140a and 140b. The apparatus also includes another electrode 144 whichis in a current flow path including the treating electrode 140 and isapplied to a location spaced from the site to be healed. In accordancewith this embodiment of the present invention, there is provided waveshaping means generally designated 146 operatively connected to thevoltage applying means 142 and to the treating electrode 140 for causingthe electrical current flow relative to the treating electrode to have awave form which is readily discernable by external patient monitoringapparatus. The wave shaping means 146 includes switching means connectedbetween the voltage applying means 142 and the treating electrode 140for alternately connecting and disconnecting the voltage applying meansto the treating electrode, and control means connected in controllingrelation to the switching means for operating, i.e. opening and closing,the switching means. In an illustrative form of wave shaping means, theswitching means includes a first transistor switch 150 having collector,base and emitter terminals 152, 154 and 156, respectively. Collectorterminal 152 is connected to the section 140a of the treating electrodeand emitter terminal 156 is connected to the section 140b of thetreating electrode. In order to accomodate flow of current in twodirections, as in the embodiment of FIG. 1, the switching means furtherincludes a second transistor switch 158 having emitter, base andcollector terminals 160, 162 and 164 respectively. Emitter terminal 160is connected to the section 140a of the treating electrode and collectorterminal 164 is connected to the section 140b of the treating electrode.The control or base terminals 154 and 162 of the transistor switches 158and 150, respectively, are connected together by a lead 166, and areconnected in turn to the output of a control means generally designated170. Control means 170 provides output control pulses which aretransmitted to the base terminals 154 and 162 for turning the transistorswitches 150 and 158 on and off at a controlled rate in a known manner.The control means 170 includes timing means 172 for controlling theduration of the control pulses. In other words, the combination of thecontrol means and timing means, which for example can be a multivibratortype circuit having RC timing control, opens and closes the transistorswitches 150 and 158 at a controlled rate. In accordance with apreferred mode of the present invention, the switches are turned on andoff about once each second with the on time duration being about twicethe length of the off time duration. The resulting current wave formthrough the treating electrode 140 has leading and trailing edges whichare clearly discernable by external patient monitoring apparatus.Voltage for operating the control means 170 in the present illustrationis obtained from component 142 by means of line 176.

In order to monitor operation of the implanted tissue growth controlapparatus, the shaped wave form of the electrical current flowingrelative to the treating electrode 140 is detected by means ofmonitoring apparatus external to the body of the patient and responsiveto the shaped wave form. For example, the leading and trailing edges ofthe on-off current wave form are clearly discernable on a conventionalECG machine. In addition, the operation of the apparatus can bemonitored on an oscilloscope provided with skin electrodes which wouldbe located on the external skin of the patient, one over the area orsite to which the treating electrode 140 is connected and the other skinelectrode over the region where the reference electrode 144 isconnected. Thus, one can readily determine that the implanted apparatuscontinues to operate. In addition, the mode of operation of theimplanted healing apparatus, i.e. be it the germicidal or the healingmode as in the embodiments illustrated in FIGS. 1-4, would be clearlydiscernable from the wave form polarity and the magnitude and/orrepetition rate of the signal detected by the apparatus. This is becausethe current flows are in opposite directions and also are of differentmagnitudes in the two modes, and in addition there could be a differentrepetition rate of the current in the germicidal and healing modes.

It is therefore apparent that the present invention accomplishes itsintended objects. While several embodiments of the present inventionhave been described in detail, this is for the purpose of illustrationand not limitation.

I claim:
 1. Apparatus for implantation in a patient for providinggermicidal and healing treatment of tissue such as bone comprising:(a)an electrode of silver adapted to be operatively connected to a livingtissue site to be healed; (b) another electrode adapted to be connectedto a location spaced from the site to be healed; (c) a source of directvoltage having positive and negative polarity output terminals; (d)switching means operatively connected to said electrodes and to saidterminals of said source, said switching means having a first statewherein said silver electrode is connected to said positive terminal andsaid other electrode is connected to said negative terminal once duringan initial portion of the time during which said silver electrode isoperatively connected to the tissue site and a second state wherein saidsilver electrode is connected to said negative terminal and said otherelectrode is connected to said positive terminal once during theremaining portion of the time during which said silver electrode isoperatively connected to the tissue site, said switching means includingmeans enabling said switching means to be operated by operator meanspositioned external to said patient at a location so as to beoperatively associated with said switching means for selectively andnon-invasively changing the states of said switching means; and (e)means for enclosing said source, said switching means, any portion ofsaid silver electrode not in operative contact with said tissue site tobe healed, and any portion of said other electrode not in operativecontact with said location spaced from the site to be healed, saidenclosing means being of human body reaction free material therebypermitting said apparatus to be implanted in the body of the patient;(f) whereby when said switching means is in said first state currentflow is in a direction relative to said silver electrode causing silverions to be released to create a germicidal environment at the tissuesite and when said switching means is in said second state current flowis in an opposite direction causing healing of tissue at the site. 2.Apparatus according to claim 1, wherein said switching means comprises apair of single pole double throw magnetic reed switches and wherein saidoperator means comprises a magnetic element operatively associated withsaid switches for selectively changing the states of said switches. 3.Apparatus according to claim 1, wherein said direct voltage sourcecomprises a battery.
 4. Apparatus according to claim 3, wherein saidbattery is of the lithium-halogen type.
 5. Apparatus according to claim1, wherein said silver electrode comprises a silver wire adapted to beinserted in the tissue site.
 6. Apparatus according to claim 1, furtherincluding first electrical resistance means connected between saidpositive source terminal and said switching means and second electricalresistance means connected between said negative source terminal andsaid switching means, said second resistance means having a magnitudesignificantly greater than the magnitude of said first resistance meanswhereby the magnitude of current flow during healing of tissue issignificantly less than the magnitude of current flow during germicidaltreatment.
 7. Apparatus according to claim 1, further including waveshaping means operatively associated with said silver electrode forcausing the electrical current flow relative to said silver electrode tohave a waveform which is readily discernible by external patientmonitoring apparatus.
 8. A method of providing germicidal and healingtreatment of tissue such as bone comprising the steps of:(a) providingapparatus comprising an electrode of silver adapted to be operativelyconnected to a living tissue site to be healed, another electrodeadapted to be connected to a location spaced from the site to be healed,a source of direct voltage having positive and negative polarity outputterminals, switching means operatively connected to said electrodes andto said terminals of said source, said switching means having a firststate wherein said silver electrode is connected to said positiveterminal and said other electrode is connected to said negative terminalonce during an initial portion of the time during which said silverelectrode is operatively connected to the tissue site and a second statewherein said silver electrode is connected to said negative terminal andsaid other electrode is connected to said positive terminal once duringthe remaining portion of the time during which said silver electrode isoperatively connected to the tissue site, and means for enclosing saidsource, said switching means, any portion of said silver electrode notin operative contact with said tissue site to be healed, and any portionof said other electrode not in operative contact with said locationspaced from the site to be healed, said enclosing means being of humanbody reaction free material whereby said apparatus is implantable in thebody of a patient; (b) implanting said apparatus in the body of apatient in neighboring relation to the tissue site to be healedincluding applying said silver electrode to the site and applying saidother electrode to a location in the body spaced from the site to behealed; (c) providing operator means having an operative associationwith said switching means for non-invasive and selective changing of thestates of said switching means; and (d) placing said operator means at aposition external to the body of a patient at a location providing saidoperative association and operating said operator means to apply to saidsilver electrode for a predetermined time and once while said silverelectrode is applied to the tissue site a d.c. voltage of a positivepolarity causing current flow in one direction to drive said silverelectrode as an anode and release ions to create a germicidalenvironment at the site and then to apply to said silver electrode aftersaid predetermined time and once while said silver electrode is appliedto the tissue site a d.c. voltage of opposite polarity causing currentflow in the opposite direction to drive said silver electrode as acathode to stimulate healing of tissue at the site.
 9. A methodaccording to claim 8, wherein said step of applying a d.c. voltage ofopposite polarity to stimulate healing is performed for a length of timesignificantly greater than said step of applying d.c. voltage to createthe germicidal environment.
 10. A method according to claim 8, furtherincluding limiting the magnitude of current flow in said oppositedirection during healing to a magnitude significantly less than themagnitude of current flow in said one direction creating the germicidalenvironment.
 11. In combination with implantable apparatus for providinggermicidal and healing treatment of tissue such as bone comprising atreating electrode of a material which creates a germicidal environmentand promotes healing of tissue in response to current flow relative tothe electrode, the germicidal or healing mode being determined by acharacteristic of said current flow, and means for applying voltage tosaid electrode to cause said current flow: wave shaping meansoperatively connected to said voltage applying means and to saidtreating electrode for causing the electrical current flow relative tosaid treating electrode to have a waveform which is readily discernibleby external patient monitoring apparatus for determining non-invasivelycontinued operation of said apparatus when implanted and the germicidalor healing treatment mode of operation of said apparatus.
 12. Thecombination according to claim 11, wherein said wave shaping meanscomprises:(a) switching means connected between said voltage applyingmeans and said treating electrode for alternately connecting anddisconnecting said voltage applying means to said treating electrode;and (b) control means connected in controlling relation to saidswitching means for opening and closing said switching means.
 13. Thecombination according to claim 12, wherein said control means includestiming means for controlling the relative time durations of opening andclosing of said switching means.
 14. A method of monitoring theoperation of apparatus implanted in a patient for healing treatment oftissue such as bone including a treating electrode of a material whichpromotes healing of tissue in response to current flow relative to theelectrode, the treating electrode being applied to a tissue site to behealed and another electrode in a current flow path including thetreating electrode being applied to a location spaced from the site tobe healed, and means for applying voltage to the treating electrode forcausing the electrical current flow relative to the treating electrode,said monitoring method comprising:(a) shaping the waveform of theelectrical current relative to the treating electrode to have a waveformwhich is readily discernible by external patient monitoring apparatus;and (b) detecting the shaped waveform non-invasively by means ofmonitoring apparatus external to the body of a patient and responsive tothe shaped waveform.
 15. The method according to claim 14, wherein saidstep of shaping the waveform comprises periodically connecting anddisconnecting the voltage applying means to the treating electrode. 16.The method according to claim 15, wherein the connecting anddisconnecting is performed at a rate of about once per second.
 17. Themethod according to claim 16 wherein the time duration of the connectingis about twice the time duration of the disconnecting.